Automatic electronic test equipment has been used to test various types of integrated circuits (“ICs”) and discrete semiconductor components.
The different types of integrated circuits have included digital ICs, linear ICs, and mixed signal ICs. Examples of digital ICs include high-speed very large scale integrated (“VLSI”) digital ICs, including microprocessors and microcontrollers. Linear ICs are also called analog ICs. Linear ICs are used, for example, to amplify, filter, or shape information such as sound, images, temperature, pressure, speed, acceleration, position, or rotation. Examples of linear ICs include amplifiers, voltage regulators, voltage detectors, operational amplifiers, clock circuits, and phase locked loops. Mixed signal ICs handle both digital and analog signals. One example of a mixed signal IC is a D to A converter that converts digital signals to analog signals. Another type of mixed signal IC is an A to D converter that converts analog signals to digital signals.
Different prior art automatic test equipment has been used to test different categories of ICs. Digital automatic test systems have been used to test digital ICs. Linear/mixed signal automatic test systems have been used to test linear and mixed signal ICs.
One example of a prior art digital test system is the Micromaster™ sold by LTX Corporation of Westwood, Mass. The Micromaster is designed for testing high performance CISC (complex instruction set computing) and RISC (reduced instruction set computing) microprocessors and the digital ICs that make up the chip sets that are used with the microprocessors.
One example of a prior art linear/mixed signal test system is the Synchro™ test system sold by LTX Corporation of Westwood, Mass. The Synchro automatic test system is designed for high throughput testing of linear ICs and for testing of mixed signal ICs that require lower digital pattern rates and moderate digital pin counts. The Synchro tester includes independent microprocessors that concurrently control each test instrument applied to the device under test (i.e., the IC under test). This design permits the generation of test signals and measurements on many device pins at the same time in order to speed up test times on high complexity ICs.
Trends in technology have resulted in more circuits, transistors, and other devices being placed on integrated circuits. In other words, the level of chip integration has risen. Because of this, a new category of integrated circuit has arisen, called the system-on-a-chip ICs. System-on-a-chip ICs are also referred to as multifunction ICs or multifunction devices. The system-on-a-chip ICs integrate fundamentally different IC subsystems on the same piece of silicon. These IC subsystems include VLSI logic cores, embedded memory, and mixed signal interfaces. Thus, system-on-chip ICs can incorporate digital circuitry, analog circuitry, and memory circuitry on a single chip. These subsystems were once available only on a circuit board populated with discrete devices, but now are placed on a single IC. One example of a system-on-a-chip is the Riva™ 128 graphics controller sold by nVidia, Inc., Inc. of Santa Clara, Calif. The Riva 128 is a single chip implementation of a graphics accelerator that digitally manipulates video images and then transmits them in analog form to either a computer or a television monitor.
One disadvantage of the prior art automatic electronic testers is that no single tester has the performance required to test a broad range of digital ICs, analog/mixed signal ICs, and memory ICs. To test a broad range of such types of ICs, a company would have to purchase at least two types of testers and train personnel to use at least two types of testers.
Prior art digital testers and prior art linear/mixed signal testers typically have some complementary technology, however. The prior art linear/mixed signal testers typically have some limited digital testing capability. The prior art digital testers typically have some limited analog capability. Nevertheless, complementary capabilities of both types of testers is extremely limited. Furthermore, the two types of testers are typically incompatible. This can result in higher cost of operation because test equipment is underutilized when the device that the tester can exclusively test is not being produced.
As a result, the primary disadvantage of prior art electronic test equipment is that a single platform tester cannot fully test the full spectrum of ICs, including some of the more complex ICs that have a high level of integration, such as some newer system-on-a-chip ICs. In other words, one would have to use both a digital automatic electronic tester and a linear/mixed signal automatic electronic tester to fully test certain complex multifunction ICs. Using two testers is typically relatively expensive, cumbersome, and time consuming as opposed to using a single tester. Not only is there the added expense of two machines rather than one, but typically corporations have employees who are trained on one type of tester (digital or linear/mixed signal) but not the other, and vice versa. Furthermore, some tests might be extremely difficult, if not impossible, to perform on two separate testers sequentially if there is high level of integration between analog circuitry and high speed digital circuitry on a single chip. Moreover, in certain instances, prior art testers are not capable of testing the new types of functions performed by single multifunction ICs, especially those functions that occur at increasingly high speeds.